The quality control of plastic injection molding machines, die casting machines, and others depends on the alignment of a movable platen with a parallel stationary platen. The movable platen is slidable on slender cylindrical tie bars, each of which is rigidly attached at end portions. Dies or molds which are mounted on the platens are opened and closed by sliding the movable platens on the tie bars.
If tie bars are not straight or at right angles to the fixed platens, platen misalignment occurs, causing the dies or molds to be misaligned and part quality to deteriorate.
Poor part quality adversely affects a manufacturer's reputation, increases its warranty costs and sometimes results in an expensive product recall. It can also increase manufacturing costs by requiring secondary operations and increase machine wear, causing additional maintenance and lost production.
Inspections of tie bar squareness and straightness with mechanical equipment, such as dial indicators, is difficult and time consuming. In our pending U.S. application Ser. No. 08/286,342, a laser apparatus and method were disclosed for inspecting the alignment of the movable platen with the fixed or stationary platen. If platens are found to be misaligned, the cause of the misalignment must be identified.
A need exists for inspecting tie bars, a common source of platen misalignment. Inspections of tie bar straightness and squareness, with mechanical equipment such as dial indicators is difficult and time consuming because of set-up times and lengths of the tie bars.
Some manufacturers are reluctant to inspect tie bar straightness and squareness because it is difficult and time consuming. Instead, part quality is sacrificed, machines obsoleted or expensive tie bar teardown and rebuilding (T & R) procedures are performed. Expensive T & R's could be avoided if an effective and easy to use apparatus was available for inspecting the tie bars.
An effective and easy to use apparatus for inspecting tie bars would also assist a manufacturer in planning and scheduling machine maintenance. It would also assist a manufacturer of machinery in maintaining quality control.